The 20DP-K-30 Differential Pressure Swichgage with Rigid Contact is a 2" dual-scale dial, diaphragm-actuated differential pressure-indicating gage, with a built in electrical switch. This switch, typically used for sand filtered drip irrigation applications, is used for tripping alarms and/or shutting down equipment. An adjustable knob ("K") is used to dial in your predetermined set point. During episodes of high differential pressure, whether pressure is building or spiking, the "rigid limit contact" design ensures that your gage will maintain the desired set point. On this model, the gage pointer acts as a pressure indicator and as one switch pole which completes a circuit when it touches the adjustable rigid limit contact. Contacts are grounded through the case and have a self-cleaning motion to ensure electrical continuity. The 20DP-K-30, with a pressure range of 0-30 psi, is intended to monitor and indicate oil, fuel or water filter restriction and can reduce the risk of dangerously high pressure which may rupture the filter, resulting in contaminants entering the system. This filter restriction Swichgage will let you know when to change your filter and maintain peak efficiency. The gage mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, break-resistant lens and a polished, stainless steel bezel help protect this rugged instrument.